1. Field of the Invention
The present invention relates to a disc having friction liners for a mechanical clutch, the disc including in its peripheral region, surrounding its central portion, fastening zones which are generally parallel to the plane of the central portion, firstly for a first liner which is annular or divided into pads, and which is arranged to make frictional contact with the pressure plate of the clutch, and secondly for a second liner, which is also annular or divided into pads, and which is arranged to make frictional contact with the reaction plate of the clutch.
The peripheral region of the disc may be annular and continuous, but it is currently divided into radial blades carrying the above mentioned fastening zones, these blades being joined to the central portion of the disc through a foot and serving alternately for the fastening of the first liner and for the fastening of the second liner.
The blades may be integral with the central portion of the disc, or they may be attached to it by means of rivets. The blades on which one liner is to be fixed may be of a different form from the blades on which the other liner is to be fixed, and these forms may in themselves be very varied, according to the effect which is required, or manufacturing requirements.
The blades may also all be of the same form, for example that of a curtain, and they may be bent in one direction and in the other so that they themselves have fastening zones which serve for the alternate fastening of one of the liners and the other liner.
2. Description of the Prior Art
Examples of blades of these different types are given in the documents EP-A-0 579 554 (U.S. Pat. No. 5,452,783) and FR-A-2 370 893. In order to increase the rigidity of the fastening of the liners, and so as to obtain more regular wear in the liners without fretting, it is common practice, and is the case in the two documents mentioned above, to provide on each blade, for example on either side of the zone in which it is fastened on the liner concerned, supplementary engagement zones which are offset axially towards the other liner and which are able to engage with the latter.
That being so, the function of such a disc, where the latter is art of a clutch friction wheel of a mechanical clutch, the most common application of which is of course in the automotive field, is sufficiently well known by the engineer in this field for there to be no need to describe it in detail. It will be enough to recall (FIG. 7) that, when the clutch pedal is released, the two liners 101, 102 of the disc 100 are under load and are solidly coupled, by being gripped between the pressure plate 103 and the reaction plate 104, to the pressure plate and reaction plate so as to rotate with these latter, the reaction plate being driven by the crankshaft of the engine. The disc 100 carrying the liners therefore drives, either through interposed springs 107 or directly, a radial plate 105 which meshes, with or without a circumferential clearance, with a central hub 106 which is itself in engagement with the input shaft of the gearbox, so that the latter is in consequence driven by the crankshaft. Such a mode of operation is described in Application PCT/FR94/00297 (WO94/21934), which also discloses a large number of versions of forms of radial blades, including tripod blades.
In one embodiment of the Application WO-A-94/21934, fastening of the liners is obtained by adhesive bonding, and the peripheral region includes blades having bending lines which separate a central zone, defining a fastening zone, from supplementary engagement zones.
The liners are adhesively bonded on the central zone of the blades.
The central zones of the blades are raised with respect to the central portion of the disc, due to the fact that they are offset axially with respect to the central portion.